Table 3.
Linear mixed effects models for change in urinary biomarkers of kidney injury among sugarcane workers
| All Workers (N=284) |
Restricted to Men (n=251) |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| NGAL, ln(μg/g) | IL-18, ln(ng/g) | NAG, ln(U/g) | NGAL, ln(μg/g) | IL-18, ln(ng/g) | NAG, ln(U/g) | |||||||
|
|
||||||||||||
| Model 1 a | ||||||||||||
| Job setting | ||||||||||||
| Field worker | 1.49 (1.06-2.09) | 1.61 | (1.12, 2.31) | 2.92 | (2.08, 4.10) | 1.73 | (1.22, 2.44) | 1.66 | (1.14, 2.42) | 2.88 | (1.99, 4.16) | |
| Non-field worker | ref | ref | ref | ref | ref | ref | ||||||
| Sex | ||||||||||||
| Male | 0.38 | (0.27, 0.53) | 0.38 | (0.27, 0.51) | 0.85 | (0.59, 1.22) | - | - | - | |||
| Female | ref | ref | ref | - | - | - | ||||||
| Model 2 b | ||||||||||||
| Job | ||||||||||||
| Cane cutter | 2.57 | (1.54, 4.27) | 1.89 | (1.08, 3.29) | 4.92 | (2.94, 8.23) | 2.67 | (1.62, 4.41) | 1.93 | (1.10, 3.37) | 4.90 | (2.86, 8.39) |
| Seeder | 1.00 | (0.57, 1.76) | 2.11 | (1.14, 3.92) | 4.38 | (2.47, 7.77) | 1.50 | (0.69, 3.23) | 3.44 | (1.46, 8.08) | 4.98 | (2.19, 11.4) |
| Seed cutter | 0.79 | (0.39, 1.58) | 1.05 | (0.49, 2.27) | 2.57 | (1.26, 5.23) | 0.65 | (0.25, 1.65) | 0.82 | (0.29, 2.33) | 1.54 | (0.56, 4.18) |
| Agrichemical applicator |
1.00 | (0.55, 1.84) | 1.19 | (0.61, 2.32) | 3.23 | (1.74, 5.97) | 1.04 | (0.57, 1.90) | 1.22 | (0.63, 2.37) | 3.21 | (1.69, 6.10) |
| Irrigator | 2.07 | (1.24, 3.47) | 1.50 | (0.86, 2.63) | 3.66 | (2.18, 6.17) | 2.16 | (1.30, 3.58) | 1.53 | (0.87, 2.70) | 3.65 | (2.12, 6.29) |
| Driver | 1.09 | (0.63, 1.88) | 0.96 | (0.53, 1.74) | 2.03 | (1.17, 3.52) | 1.13 | (0.66, 1.94) | 0.98 | (0.54, 1.79) | 2.02 | (1.14, 3.58) |
| Factory worker | ref | ref | ref | ref | ref | ref | ||||||
| Sex | ||||||||||||
| Male | 0.41 | (0.26, 0.63) | 0.34 | (0.23, 0.51) | 0.94 | (0.58, 1.51) | - | - | - | |||
| Female | ref | ref | ref | - | - | - | ||||||
Note: Values are given as relative mean (95% confidence interval); relative mean (exponentiated β coefficient; ie, e to the power of β) represents the fold-change in biomarker during the harvest compared to the reference group, as outcome variables were ln-transformed prior to analyses. For example, field workers had a mean change in NGAL concentration during the harvest that was 1.49 times as high as the change among non-field workers.
Abbreviations: NGAL, neutrophil gelatinase-associated lipocalin; IL-18, interleukin 18; NAG, N-acetyl-β-D-glucosaminidase.
Model 1: individual job categories were grouped into field workers (cane cutters, seeders, seed cutters, agrichemical applicators, and irrigators) and non-field workers (drivers and factory workers). Model parameters for each ln(outcome) include time, fieldworker status, time × fieldworker status, sex, age, and years worked. Results presented as “Change in biomarker during harvest” are the exponentiated β coefficients of the time × fieldworker status variable. Full model results and p-values are presented in Table S3.
Model 2: all job categories were analyzed individually. Model parameters for each ln(outcome) include time, job, time×job, sex, age, and years worked. Results presented as “Change in biomarker during harvest” are the exponentiated β coefficients of the time×job variable. Full model results and p-values are presented in Table S4.